1. Field of the Invention
The present invention relates to controlling the characteristics of automobile airbag module energy management. More specifically the present invention relates to an apparatus for controlling energy management characteristics of an automobile airbag module through selectively opening venting holes in the airbag housing.
2. Technical Background
Inflatable airbags are well accepted in their use in motor vehicles and have been credited with preventing numerous deaths and accidents. Some statistics estimate that frontal airbags reduce fatalities in head-on collisions by 25% among drivers using seat belts and by more than 30% among unbelted drivers. Statistics further suggest that with a combination of seat belt and airbag, serious chest injuries in frontal collisions can be reduced by 65% and serious head injuries by up to 75%. Thus, airbag use presents clear benefits.
Despite the clear benefits of current airbags, recent debate concerning the safety of airbags has occurred. Most airbags currently in use have a generically sized airbag coupled to a generic inflator. When a vehicle experiences a rapid deceleration, the inflator will inflate the airbag with a single set of deployment characteristics, regardless of the occupant""s physical characteristics. Studies have established that a single set of deployment characteristics may not be effective in restraining all occupants. For example, the deployment force of an airbag required to attenuate the motion of a large man may cause serious injury or death when that force is applied to a child or small woman.
Furthermore, the success of airbags has created the misconception that airbags may be used to replace primary restraining systems, such as seatbelts. Disregarding primary restraining systems will result in the occupant applying a larger force on the airbag than would be present if the occupant had been using a seat belt.
In order to overcome this design dilemma, intelligent airbag deployment systems have begun to appear in various vehicles. Intelligent airbag deployment systems are capable of measuring the physical characteristics and environment surrounding various passengers. Measurements such as weight, position, and presence of a passenger can be determined. Using the obtained information the airbag may be deployed and controlled accordingly. Furthermore, some systems are capable of determining if a passenger is actually in a seat and not wearing a seatbelt, or if the seat is simply empty. Yet other systems are capable of detecting the presence of a child safety seat and will not deploy at all.
However, this new approach in controlling airbag inflation brings the problem of having a single airbag that is capable of multiple deployment characteristics. Generally, an airbag module is primarily comprised of an airbag and an inflator. The inflator comprises a gas generant and is fluidly coupled to the airbag. When an initiation signal is received from a sensor in the automobile, the inflator ejects a gas into the airbag. In order to control the inflation characteristics of the airbag, the flow of gas into the airbag must be controlled.
One method of controlling the flow of gas into the airbag is to provide a controlling system situated between the inflator and the airbag. Such a system allows an inflator having generic deployment characteristics to be used. The inflator may eject a flow of gas where measured amounts of the gas is diverted away from the airbag before of after inflation of the airbag. Thus, a single inflator may be designed for the largest inflation force required and inflation of the airbag be controlled by a regulating system.
One promising system for controlling the amount energy imparted by an airbag onto a passenger is through the use of venting mechanisms. Venting mechanisms may be placed within the walls of the structure that conveys the gas from the inflator to the airbag, such as a housing. Typically, a housing is a structure that maintains the inflator and the airbag.
A venting mechanism operates by selectively venting an amount of gas away from or out of the airbag. By discharging various increments of gas away from the airbag, the inflation characteristics of the airbag and the duration of inflation can be controlled. Unfortunately, current processes and apparatuses for venting gas out of the housing and away from an airbag are often unsatisfactory. The current processes lack an efficient and controllable system for venting a gas.
Some airbag modules control the venting process through complex gas flow systems. These systems often have expensive solenoid controlled valves to measurably release varying amounts of gas. Such systems can require a large amount of design and can be unreliable. Other airbag modules implement piezoelectric crystals in place of solenoids to selectively open the venting valves in response to an electrical current. However, piezoelectric crystals are expensive and can require a large input signal to open a valve. Furthermore, these complex systems are often wasteful for a single operation airbag inflator.
Recognizing the possible benefits of a single operation airbag module, other venting systems have sought to deflagrate various shapes in the sides of the housing. To accomplish this, a channel or other mounting structure is typically molded or cut into the side of the housing. A deflagration device is then placed in the channel. Often, the channel defines the shape of a venting hole that will be deflagrated into the wall of the housing. When the deflagration strip ignites, the outline of a venting hole is created having a shape that is the same as the shaped of the deflagration strip. Thus, the high internal air pressure of the inflation gas created during deployment forces a vent to open in the housing.
While the above described system does provide advantages over complex mechanical systems, it still has several significant disadvantages. For example, deflagrating a shape into the side of a housing may not create a precisely uniform shape to vent a measured amount of gas. Further, a large deflagration will increase the cost of the airbag module. Also, the heat generated by a deflagration strip may have some adverse effects on the airbag itself. Creating channels in a housing and adding a deflagration strip can increase the manufacturing time required to make a module. Finally, attempts to deflagrate a hole through the wall of the housing may not always be successful, preventing the venting system from operating correctly.
In order to correct the shortcomings of the above described systems, what is needed is a low cost system to vent an inflation gas away from an airbag. What is also needed is a system that is small and inexpensive. Furthermore, a system is needed that uses minimal energy to vent a maximum amount of gas. Another need exists for an inflation gas venting system that can incrementally vent different amounts of gas. What is also needed is a system that insures a precisely sized venting hole for highly calibrated gas emission. What is further needed is a system that may be manufactured quickly with minimal custom made parts.
There is also a need in the art for an airbag inflation system that controllably vents gas out of an inflated airbag. There is a further need in the art for an inflation system that controllably decelerates an occupant""s impact with an airbag. A need also exists for a system that employs an occupant""s impact energy in decelerating the occupant. Such a system and method is disclosed and claimed herein.
The apparatus and method of the present invention have been developed in response to the present state-of-the-art, and, in particular, in response to need in the art. Thus, it is an overall objective of the present invention to provide a low cost and highly controllable venting system for an airbag module.
To accomplish this objective, a housing having a plurality of walls is provided. The walls define an interior and an exterior of the housing. At least one venting hole is present in a wall of the housing. The venting hole is a hole that provides fluid communication between the interior and exterior of the housing. The venting hole is sealed by a generally thin membrane, preventing fluid communication between the interior and exterior of the housing.
An initiator is located at a position relative to the membrane, such that upon initiation the initiator produces a hole in the membrane. The initiator may be directly attached to the membrane or may be spaced at a distance from the membrane. Once a hole is produced in the membrane, the internal pressure of the gas in the housing or the load placed on the airbag by the occupant forces the membrane to open. Thus, the interior and the exterior of the housing come into fluid communication again.
The membrane may have several embodiments. The membrane may include various materials, such as foils or plastics. Additionally, the various thicknesses of these materials may be used to the membranes. Similarly, the venting holes in the housing may also be various shapes, sizes, and numbers. Some venting holes may be generally circular, while others may be elongated openings. Other housings may include multiple venting holes on multiple housing walls. The additional venting holes may have individual membranes sealing them, or alternatively, a single membrane may cover multiple venting holes.
Several methods of opening the venting holes may also be incorporated in the airbag module. For example, the initiator may create only a small propagation hole in the membrane. The propagation hole provides a location from which the pressure within the housing may force open the remaining membrane. Thus, a relatively small hole in the membrane allows the pressure within the housing to fully open the entire venting hole. Other initiators may create larger propagation holes, such as a slit or xe2x80x9cXxe2x80x9d shaped cut in the membrane. Alternatively, the initiator may be configured to destructively open the entire membrane at a single instant.
Various types of initiators may be incorporated in the airbag module. The initiators may be a deflagration, electrochemical, or pyrotechnic device. These initiators may further be controlled by an impact management system. The impact management system may receive various signal inputs from sensors positioned throughout an automobile. The sensors may determine the degree of inflation and deflation required for the airbag and open a selective number of venting holes accordingly. Thus, the inflation and deflation characteristics of an airbag may be tailored to the physical characteristics and environment of individual passengers.
These and other features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.